GAZA CITY , Gaza -LRB- CNN -RRB- -- Israeli forces fired on a U.N. aid convoy Thursday in Gaza , killing at least one contract worker and prompting the U.N. to halt some of its operations in Gaza , U.N. officials said .

Palestinians distribute U.N. food aid Thursday in a refugee camp in southern Gaza .

The U.N. has `` lost confidence '' in the Israeli military 's attempts to allow humanitarian aid into the Palestinian territory , the U.N. Relief and Works Agency 's director said .

Meanwhile , the U.N. Security Council late Thursday overwhelmingly approved a resolution calling for an immediate cease-fire in Gaza .

Fourteen of the council 's 15 members voted in favor of the resolution -- with U.S. Secretary of State Condoleezza Rice abstaining from the vote .

Hours before the resolution was approved , U.N. Secretary-General Ban Ki-moon demanded an investigation into the convoy incident he said killed two contract workers near the Israel-Gaza border . UNRWA director John Ging said one aid worker was killed .

Ging expressed frustration with the Israeli military , which he said cleared the convoy to travel into Gaza . Images emerge of Israeli troops in Gaza ''

`` We are perfectly willing to take risks , but something has to change , '' Ging told reporters from Gaza City . `` If they give us the clearance to move , it is -LSB- unacceptable -RSB- that their soldiers are firing on us from the ground . ''

Ging said an Israeli liaison did not dispute that Israeli forces fired on the vehicle . Four U.N. staffers have been killed since Israeli airstrikes on Gaza began December 27 , and two U.N. schools in the territory used as civilian shelters have also been hit by the Israeli military .

The aid agency provides food and relief supplies to some 80 percent of Gaza 's 1.5 million people , but it says it has been unable to reach many Palestinians or assess the situation in Gaza during the Israeli military offensive .

The absence of foreign journalists -- whom Israel has barred from entering Gaza -- is preventing the truth about conditions there from getting out , Ging said .

`` We have horrific stories coming out now . ... You have to brace yourself for more , '' Ging said . `` This is a horrific situation . ''

Red Cross workers on Wednesday found numerous wounded Palestinians in the neighborhood of Zaytun , the organization said in a statement . The injured included four children , too weak to stand , next to their dead mothers in a house containing 12 corpses , the International Committee of the Red Cross said .

Palestinian medical sources said Thursday that 765 Palestinians have died in Gaza -- nearly 40 percent of them women and children -- since the Israeli military operation began . Three Israeli soldiers died in the fighting on Thursday , bringing to 10 the number of Israeli soldiers killed in the operation .

Three Israeli civilians and one of those soldiers have been killed in rocket strikes from Gaza .

The Israeli military says its operation is aimed at halting the firing of rockets into southern Israel by Hamas , which has controlled Gaza since 2007 . But militants have continued to fire dozens of rockets and mortar shells on southern Israel since Israel launched its military operation .

More than 20 rockets were fired into Israel on Thursday , Israeli police said .

The mounting death toll and humanitarian concerns in Gaza are being addressed by cease-fire proposals now being considered by Israeli and Palestinian diplomats in Egypt .

Israel continued its military operations in Gaza even during a three-hour period in which it said it would halt its offensive activities to allow for `` humanitarian activities . ''

At least 50 trucks carrying aid were allowed into Gaza on Thursday , but it is unclear if any of the supplies were distributed to civilians .

Much of the U.N. 's aid is stuck at the Kerem Shalom border crossing because the private company that drives the aid in is refusing to enter Gaza `` because the situation is too dangerous , '' U.N. Humanitarian Affairs chief John Holmes said .

Israel has periodically opened some of its borders with Gaza to allow aid into the territory during the military campaign .

Ambulance crews struggled Thursday to deliver patients through the Gaza-Egypt crossing , drivers said . Mohammed Hamid , a Palestinian driver , told CNN Israeli forces are stopping ambulances evacuating the wounded . Watch driver say Israelis are blocking ambulances ''

During the three-hour `` truce '' on Thursday , large explosions could be heard from central Gaza and small arms fire from northern Gaza , according to CNN 's Ben Wedeman , reporting from along the Israel-Gaza border .

Also , Israeli armored bulldozers demolished a home in Gaza `` just as the lull was supposed to go into effect , '' he said .

Video shot from the border showed the home -- with two white flags flying on the roof -- crumble to the ground as the bulldozers plowed into its side and roll over the debris .

`` We saw a man coming out of that house with a white flag and until now we have seen no sign of any military activity in that area , '' Wedeman reported . `` There have been no shots fired from that house . ''

The Israeli military had no comment on the incident . A three-hour truce on Wednesday was also marred by fighting which Israeli officials said were in retaliation for Hamas attacks on Israeli forces .

Separately , four rockets fired from southern Lebanon landed near the northern Israeli city of Nahariya Thursday , leaving two people with minor injuries . The Israeli military returned fire across the border and suggested that residents of northern Israel stay near their shelters . Watch CNN 's Christiane Amanpour discuss the rocket attacks ''

There was no immediate claim of responsibility . Hezbollah assured the Lebanese government that it was not responsible for the attacks , the Lebanese information minister said .

Hezbollah has kept a tight rein on its forces in southern Lebanon since the cease-fire following its war with Israel in 2006 . A number of Palestinian factions operate in southern Lebanon as well .

CNN 's Talal Abu Rahma , Michal Zippori , Ben Brumfield , Terrence Burke and Richard Roth contributed to this report .

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U.N. secretary-general says Israelis fired on U.N. aid convoy

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U.N. suspends some aid work , citing death of at least one worker

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Four rockets fired from southern Lebanon landed in northern Israel on Thursday

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U.N. Security Council approves resolution calling for cease-fire